- Test m_pkthdr.fw_flags against DUMMYNET_MBUF_TAGGED before trying to locate

[dragonfly/netmp.git] / sys / netinet / ip_input.c

/*
 * Copyright (c) 2003, 2004 Jeffrey M. Hsu.  All rights reserved.
 * Copyright (c) 2003, 2004 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Jeffrey M. Hsu.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
 * $FreeBSD: src/sys/netinet/ip_input.c,v 1.130.2.52 2003/03/07 07:01:28 silby Exp $
 * $DragonFly: src/sys/netinet/ip_input.c,v 1.90 2008/08/23 04:12:23 sephe Exp $
 */

#define _IP_VHL

#include "opt_bootp.h"
#include "opt_ipfw.h"
#include "opt_ipdn.h"
#include "opt_ipdivert.h"
#include "opt_ipfilter.h"
#include "opt_ipstealth.h"
#include "opt_ipsec.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/mpipe.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/globaldata.h>
#include <sys/thread.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>
#include <sys/in_cksum.h>

#include <machine/stdarg.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/pfil.h>
#include <net/route.h>
#include <net/netisr.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>

#include <sys/thread2.h>
#include <sys/msgport2.h>
#include <net/netmsg2.h>

#include <sys/socketvar.h>

#include <net/ipfw/ip_fw.h>
#include <net/dummynet/ip_dummynet.h>

#ifdef IPSEC
#include <netinet6/ipsec.h>
#include <netproto/key/key.h>
#endif

#ifdef FAST_IPSEC
#include <netproto/ipsec/ipsec.h>
#include <netproto/ipsec/key.h>
#endif

int rsvp_on = 0;
static int ip_rsvp_on;
struct socket *ip_rsvpd;

int ipforwarding = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_FORWARDING, forwarding, CTLFLAG_RW,
    &ipforwarding, 0, "Enable IP forwarding between interfaces");

static int ipsendredirects = 1; /* XXX */
SYSCTL_INT(_net_inet_ip, IPCTL_SENDREDIRECTS, redirect, CTLFLAG_RW,
    &ipsendredirects, 0, "Enable sending IP redirects");

int ip_defttl = IPDEFTTL;
SYSCTL_INT(_net_inet_ip, IPCTL_DEFTTL, ttl, CTLFLAG_RW,
    &ip_defttl, 0, "Maximum TTL on IP packets");

static int ip_dosourceroute = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
    &ip_dosourceroute, 0, "Enable forwarding source routed IP packets");

static int ip_acceptsourceroute = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
    CTLFLAG_RW, &ip_acceptsourceroute, 0,
    "Enable accepting source routed IP packets");

static int ip_keepfaith = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_KEEPFAITH, keepfaith, CTLFLAG_RW,
    &ip_keepfaith, 0,
    "Enable packet capture for FAITH IPv4->IPv6 translator daemon");

static int nipq = 0;    /* total # of reass queues */
static int maxnipq;
SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragpackets, CTLFLAG_RW,
    &maxnipq, 0,
    "Maximum number of IPv4 fragment reassembly queue entries");

static int maxfragsperpacket;
SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragsperpacket, CTLFLAG_RW,
    &maxfragsperpacket, 0,
    "Maximum number of IPv4 fragments allowed per packet");

static int ip_sendsourcequench = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, sendsourcequench, CTLFLAG_RW,
    &ip_sendsourcequench, 0,
    "Enable the transmission of source quench packets");

int ip_do_randomid = 1;
SYSCTL_INT(_net_inet_ip, OID_AUTO, random_id, CTLFLAG_RW,
    &ip_do_randomid, 0,
    "Assign random ip_id values");      
/*
 * XXX - Setting ip_checkinterface mostly implements the receive side of
 * the Strong ES model described in RFC 1122, but since the routing table
 * and transmit implementation do not implement the Strong ES model,
 * setting this to 1 results in an odd hybrid.
 *
 * XXX - ip_checkinterface currently must be disabled if you use ipnat
 * to translate the destination address to another local interface.
 *
 * XXX - ip_checkinterface must be disabled if you add IP aliases
 * to the loopback interface instead of the interface where the
 * packets for those addresses are received.
 */
static int ip_checkinterface = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, check_interface, CTLFLAG_RW,
    &ip_checkinterface, 0, "Verify packet arrives on correct interface");

#ifdef DIAGNOSTIC
static int ipprintfs = 0;
#endif

extern  struct domain inetdomain;
extern  struct protosw inetsw[];
u_char  ip_protox[IPPROTO_MAX];
struct  in_ifaddrhead in_ifaddrheads[MAXCPU];   /* first inet address */
struct  in_ifaddrhashhead *in_ifaddrhashtbls[MAXCPU];
                                                /* inet addr hash table */
u_long  in_ifaddrhmask;                         /* mask for hash table */

struct ip_stats ipstats_percpu[MAXCPU];
#ifdef SMP
static int
sysctl_ipstats(SYSCTL_HANDLER_ARGS)
{
        int cpu, error = 0;

        for (cpu = 0; cpu < ncpus; ++cpu) {
                if ((error = SYSCTL_OUT(req, &ipstats_percpu[cpu],
                                        sizeof(struct ip_stats))))
                        break;
                if ((error = SYSCTL_IN(req, &ipstats_percpu[cpu],
                                       sizeof(struct ip_stats))))
                        break;
        }

        return (error);
}
SYSCTL_PROC(_net_inet_ip, IPCTL_STATS, stats, (CTLTYPE_OPAQUE | CTLFLAG_RW),
    0, 0, sysctl_ipstats, "S,ip_stats", "IP statistics");
#else
SYSCTL_STRUCT(_net_inet_ip, IPCTL_STATS, stats, CTLFLAG_RW,
    &ipstat, ip_stats, "IP statistics");
#endif

/* Packet reassembly stuff */
#define IPREASS_NHASH_LOG2      6
#define IPREASS_NHASH           (1 << IPREASS_NHASH_LOG2)
#define IPREASS_HMASK           (IPREASS_NHASH - 1)
#define IPREASS_HASH(x,y)                                               \
    (((((x) & 0xF) | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)

static struct ipq ipq[IPREASS_NHASH];

#ifdef IPCTL_DEFMTU
SYSCTL_INT(_net_inet_ip, IPCTL_DEFMTU, mtu, CTLFLAG_RW,
    &ip_mtu, 0, "Default MTU");
#endif

#ifdef IPSTEALTH
static int ipstealth = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, stealth, CTLFLAG_RW, &ipstealth, 0, "");
#else
static const int ipstealth = 0;
#endif


/* Firewall hooks */
ip_fw_chk_t *ip_fw_chk_ptr;
ip_fw_dn_io_t *ip_fw_dn_io_ptr;
int ip_fw_loaded;
int fw_enable = 1;
int fw_one_pass = 1;

struct pfil_head inet_pfil_hook;

/*
 * XXX this is ugly -- the following two global variables are
 * used to store packet state while it travels through the stack.
 * Note that the code even makes assumptions on the size and
 * alignment of fields inside struct ip_srcrt so e.g. adding some
 * fields will break the code. This needs to be fixed.
 *
 * We need to save the IP options in case a protocol wants to respond
 * to an incoming packet over the same route if the packet got here
 * using IP source routing.  This allows connection establishment and
 * maintenance when the remote end is on a network that is not known
 * to us.
 */
static int ip_nhops = 0;

static  struct ip_srcrt {
        struct  in_addr dst;                    /* final destination */
        char    nop;                            /* one NOP to align */
        char    srcopt[IPOPT_OFFSET + 1];       /* OPTVAL, OLEN and OFFSET */
        struct  in_addr route[MAX_IPOPTLEN/sizeof(struct in_addr)];
} ip_srcrt;

static MALLOC_DEFINE(M_IPQ, "ipq", "IP Fragment Management");
static struct malloc_pipe ipq_mpipe;

static void             save_rte(u_char *, struct in_addr);
static int              ip_dooptions(struct mbuf *m, int, struct sockaddr_in *);
static void             ip_freef(struct ipq *);
static void             ip_input_handler(struct netmsg *);
static struct mbuf      *ip_reass(struct mbuf *, u_int32_t *);

/*
 * IP initialization: fill in IP protocol switch table.
 * All protocols not implemented in kernel go to raw IP protocol handler.
 */
void
ip_init(void)
{
        struct protosw *pr;
        int i;
#ifdef SMP
        int cpu;
#endif

        /*
         * Make sure we can handle a reasonable number of fragments but
         * cap it at 4000 (XXX).
         */
        mpipe_init(&ipq_mpipe, M_IPQ, sizeof(struct ipq),
                    IFQ_MAXLEN, 4000, 0, NULL);
        for (i = 0; i < ncpus; ++i) {
                TAILQ_INIT(&in_ifaddrheads[i]);
                in_ifaddrhashtbls[i] =
                        hashinit(INADDR_NHASH, M_IFADDR, &in_ifaddrhmask);
        }
        pr = pffindproto(PF_INET, IPPROTO_RAW, SOCK_RAW);
        if (pr == NULL)
                panic("ip_init");
        for (i = 0; i < IPPROTO_MAX; i++)
                ip_protox[i] = pr - inetsw;
        for (pr = inetdomain.dom_protosw;
             pr < inetdomain.dom_protoswNPROTOSW; pr++)
                if (pr->pr_domain->dom_family == PF_INET &&
                    pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW)
                        ip_protox[pr->pr_protocol] = pr - inetsw;

        inet_pfil_hook.ph_type = PFIL_TYPE_AF;
        inet_pfil_hook.ph_af = AF_INET;
        if ((i = pfil_head_register(&inet_pfil_hook)) != 0) {
                kprintf("%s: WARNING: unable to register pfil hook, "
                        "error %d\n", __func__, i);
        }

        for (i = 0; i < IPREASS_NHASH; i++)
            ipq[i].next = ipq[i].prev = &ipq[i];

        maxnipq = nmbclusters / 32;
        maxfragsperpacket = 16;

        ip_id = time_second & 0xffff;

        /*
         * Initialize IP statistics counters for each CPU.
         *
         */
#ifdef SMP
        for (cpu = 0; cpu < ncpus; ++cpu) {
                bzero(&ipstats_percpu[cpu], sizeof(struct ip_stats));
        }
#else
        bzero(&ipstat, sizeof(struct ip_stats));
#endif

        netisr_register(NETISR_IP, ip_mport_in, ip_input_handler);
}

/*
 * XXX watch out this one. It is perhaps used as a cache for
 * the most recently used route ? it is cleared in in_addroute()
 * when a new route is successfully created.
 */
struct route ipforward_rt[MAXCPU];

/* Do transport protocol processing. */
static void
transport_processing_oncpu(struct mbuf *m, int hlen, struct ip *ip)
{
        /*
         * Switch out to protocol's input routine.
         */
        (*inetsw[ip_protox[ip->ip_p]].pr_input)(m, hlen, ip->ip_p);
}

static void
transport_processing_handler(netmsg_t netmsg)
{
        struct netmsg_packet *pmsg = (struct netmsg_packet *)netmsg;
        struct ip *ip;
        int hlen;

        ip = mtod(pmsg->nm_packet, struct ip *);
        hlen = pmsg->nm_netmsg.nm_lmsg.u.ms_result;

        transport_processing_oncpu(pmsg->nm_packet, hlen, ip);
        /* netmsg was embedded in the mbuf, do not reply! */
}

static void
ip_input_handler(struct netmsg *msg0)
{
        struct mbuf *m = ((struct netmsg_packet *)msg0)->nm_packet;

        ip_input(m);
        /* msg0 was embedded in the mbuf, do not reply! */
}

/*
 * IP input routine.  Checksum and byte swap header.  If fragmented
 * try to reassemble.  Process options.  Pass to next level.
 */
void
ip_input(struct mbuf *m)
{
        struct ip *ip;
        struct in_ifaddr *ia = NULL;
        struct in_ifaddr_container *iac;
        int i, hlen, checkif;
        u_short sum;
        struct in_addr pkt_dst;
        u_int32_t divert_info = 0;              /* packet divert/tee info */
        struct ip_fw_args args;
        boolean_t using_srcrt = FALSE;          /* forward (by PFIL_HOOKS) */
        boolean_t needredispatch = FALSE;
        struct in_addr odst;                    /* original dst address(NAT) */
        struct m_tag *mtag;
        struct sockaddr_in *next_hop = NULL;
#ifdef FAST_IPSEC
        struct tdb_ident *tdbi;
        struct secpolicy *sp;
        int error;
#endif

        args.eh = NULL;
        args.oif = NULL;
        args.rule = NULL;

        M_ASSERTPKTHDR(m);

        if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
                /* Next hop */
                mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
                KKASSERT(mtag != NULL);
                next_hop = m_tag_data(mtag);
        }

        if (m->m_pkthdr.fw_flags & DUMMYNET_MBUF_TAGGED) {
                /* Extract info from dummynet tag */
                mtag = m_tag_find(m, PACKET_TAG_DUMMYNET, NULL);
                KKASSERT(mtag != NULL);
                args.rule = ((struct dn_pkt *)m_tag_data(mtag))->dn_priv;
                KKASSERT(args.rule != NULL);

                m_tag_delete(m, mtag);
                m->m_pkthdr.fw_flags &= ~DUMMYNET_MBUF_TAGGED;

                /* dummynet already filtered us */
                ip = mtod(m, struct ip *);
                hlen = IP_VHL_HL(ip->ip_vhl) << 2;
                goto iphack;
        }

        ipstat.ips_total++;

        /* length checks already done in ip_demux() */
        KASSERT(m->m_len >= sizeof(ip), ("IP header not in one mbuf"));

        ip = mtod(m, struct ip *);

        if (IP_VHL_V(ip->ip_vhl) != IPVERSION) {
                ipstat.ips_badvers++;
                goto bad;
        }

        hlen = IP_VHL_HL(ip->ip_vhl) << 2;
        /* length checks already done in ip_demux() */
        KASSERT(hlen >= sizeof(struct ip), ("IP header len too small"));
        KASSERT(m->m_len >= hlen, ("packet shorter than IP header length"));

        /* 127/8 must not appear on wire - RFC1122 */
        if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
            (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
                if (!(m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK)) {
                        ipstat.ips_badaddr++;
                        goto bad;
                }
        }

        if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) {
                sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
        } else {
                if (hlen == sizeof(struct ip)) {
                        sum = in_cksum_hdr(ip);
                } else {
                        sum = in_cksum(m, hlen);
                }
        }
        if (sum != 0) {
                ipstat.ips_badsum++;
                goto bad;
        }

#ifdef ALTQ
        if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) {
                /* packet is dropped by traffic conditioner */
                return;
        }
#endif
        /*
         * Convert fields to host representation.
         */
        ip->ip_len = ntohs(ip->ip_len);
        if (ip->ip_len < hlen) {
                ipstat.ips_badlen++;
                goto bad;
        }
        ip->ip_off = ntohs(ip->ip_off);

        /*
         * Check that the amount of data in the buffers
         * is as at least much as the IP header would have us expect.
         * Trim mbufs if longer than we expect.
         * Drop packet if shorter than we expect.
         */
        if (m->m_pkthdr.len < ip->ip_len) {
                ipstat.ips_tooshort++;
                goto bad;
        }
        if (m->m_pkthdr.len > ip->ip_len) {
                if (m->m_len == m->m_pkthdr.len) {
                        m->m_len = ip->ip_len;
                        m->m_pkthdr.len = ip->ip_len;
                } else
                        m_adj(m, ip->ip_len - m->m_pkthdr.len);
        }
#if defined(IPSEC) && !defined(IPSEC_FILTERGIF)
        /*
         * Bypass packet filtering for packets from a tunnel (gif).
         */
        if (ipsec_gethist(m, NULL))
                goto pass;
#endif

        /*
         * IpHack's section.
         * Right now when no processing on packet has done
         * and it is still fresh out of network we do our black
         * deals with it.
         * - Firewall: deny/allow/divert
         * - Xlate: translate packet's addr/port (NAT).
         * - Pipe: pass pkt through dummynet.
         * - Wrap: fake packet's addr/port <unimpl.>
         * - Encapsulate: put it in another IP and send out. <unimp.>
         */

iphack:

        /*
         * Run through list of hooks for input packets.
         *
         * NB: Beware of the destination address changing (e.g.
         *     by NAT rewriting). When this happens, tell
         *     ip_forward to do the right thing.
         */
        if (pfil_has_hooks(&inet_pfil_hook)) {
                odst = ip->ip_dst;
                if (pfil_run_hooks(&inet_pfil_hook, &m,
                    m->m_pkthdr.rcvif, PFIL_IN)) {
                        return;
                }
                if (m == NULL)                  /* consumed by filter */
                        return;
                ip = mtod(m, struct ip *);
                using_srcrt = (odst.s_addr != ip->ip_dst.s_addr);
        }

        if (fw_enable && IPFW_LOADED) {
                /*
                 * If we've been forwarded from the output side, then
                 * skip the firewall a second time
                 */
                if (next_hop != NULL)
                        goto ours;

                args.m = m;
                i = ip_fw_chk_ptr(&args);
                m = args.m;

                if ((i & IP_FW_PORT_DENY_FLAG) || m == NULL) {  /* drop */
                        if (m != NULL)
                                m_freem(m);
                        return;
                }
                ip = mtod(m, struct ip *);      /* just in case m changed */

                if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
                        mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
                        KKASSERT(mtag != NULL);
                        next_hop = m_tag_data(mtag);
                }

                if (i == 0 && next_hop == NULL) /* common case */
                        goto pass;
                if (i & IP_FW_PORT_DYNT_FLAG) {
                        /* Send packet to the appropriate pipe */
                        ip_fw_dn_io_ptr(m, i&0xffff, DN_TO_IP_IN, &args);
                        return;
                }
#ifdef IPDIVERT
                if (i != 0 && !(i & IP_FW_PORT_DYNT_FLAG)) {
                        /* Divert or tee packet */
                        divert_info = i;
                        goto ours;
                }
#endif
                if (i == 0 && next_hop != NULL)
                        goto pass;
                /*
                 * if we get here, the packet must be dropped
                 */
                m_freem(m);
                return;
        }
pass:

        /*
         * Process options and, if not destined for us,
         * ship it on.  ip_dooptions returns 1 when an
         * error was detected (causing an icmp message
         * to be sent and the original packet to be freed).
         */
        ip_nhops = 0;           /* for source routed packets */
        if (hlen > sizeof(struct ip) && ip_dooptions(m, 0, next_hop))
                return;

        /* greedy RSVP, snatches any PATH packet of the RSVP protocol and no
         * matter if it is destined to another node, or whether it is
         * a multicast one, RSVP wants it! and prevents it from being forwarded
         * anywhere else. Also checks if the rsvp daemon is running before
         * grabbing the packet.
         */
        if (rsvp_on && ip->ip_p == IPPROTO_RSVP)
                goto ours;

        /*
         * Check our list of addresses, to see if the packet is for us.
         * If we don't have any addresses, assume any unicast packet
         * we receive might be for us (and let the upper layers deal
         * with it).
         */
        if (TAILQ_EMPTY(&in_ifaddrheads[mycpuid]) &&
            !(m->m_flags & (M_MCAST | M_BCAST)))
                goto ours;

        /*
         * Cache the destination address of the packet; this may be
         * changed by use of 'ipfw fwd'.
         */
        pkt_dst = next_hop ? next_hop->sin_addr : ip->ip_dst;

        /*
         * Enable a consistency check between the destination address
         * and the arrival interface for a unicast packet (the RFC 1122
         * strong ES model) if IP forwarding is disabled and the packet
         * is not locally generated and the packet is not subject to
         * 'ipfw fwd'.
         *
         * XXX - Checking also should be disabled if the destination
         * address is ipnat'ed to a different interface.
         *
         * XXX - Checking is incompatible with IP aliases added
         * to the loopback interface instead of the interface where
         * the packets are received.
         */
        checkif = ip_checkinterface &&
                  !ipforwarding &&
                  m->m_pkthdr.rcvif != NULL &&
                  !(m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) &&
                  next_hop == NULL;

        /*
         * Check for exact addresses in the hash bucket.
         */
        LIST_FOREACH(iac, INADDR_HASH(pkt_dst.s_addr), ia_hash) {
                ia = iac->ia;

                /*
                 * If the address matches, verify that the packet
                 * arrived via the correct interface if checking is
                 * enabled.
                 */
                if (IA_SIN(ia)->sin_addr.s_addr == pkt_dst.s_addr &&
                    (!checkif || ia->ia_ifp == m->m_pkthdr.rcvif))
                        goto ours;
        }
        ia = NULL;

        /*
         * Check for broadcast addresses.
         *
         * Only accept broadcast packets that arrive via the matching
         * interface.  Reception of forwarded directed broadcasts would
         * be handled via ip_forward() and ether_output() with the loopback
         * into the stack for SIMPLEX interfaces handled by ether_output().
         */
        if (m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST) {
                struct ifaddr_container *ifac;

                TAILQ_FOREACH(ifac, &m->m_pkthdr.rcvif->if_addrheads[mycpuid],
                              ifa_link) {
                        struct ifaddr *ifa = ifac->ifa;

                        if (ifa->ifa_addr == NULL) /* shutdown/startup race */
                                continue;
                        if (ifa->ifa_addr->sa_family != AF_INET)
                                continue;
                        ia = ifatoia(ifa);
                        if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
                                                                pkt_dst.s_addr)
                                goto ours;
                        if (ia->ia_netbroadcast.s_addr == pkt_dst.s_addr)
                                goto ours;
#ifdef BOOTP_COMPAT
                        if (IA_SIN(ia)->sin_addr.s_addr == INADDR_ANY)
                                goto ours;
#endif
                }
        }
        if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
                struct in_multi *inm;

                if (ip_mrouter != NULL) {
                        /*
                         * If we are acting as a multicast router, all
                         * incoming multicast packets are passed to the
                         * kernel-level multicast forwarding function.
                         * The packet is returned (relatively) intact; if
                         * ip_mforward() returns a non-zero value, the packet
                         * must be discarded, else it may be accepted below.
                         */
                        if (ip_mforward != NULL &&
                            ip_mforward(ip, m->m_pkthdr.rcvif, m, NULL) != 0) {
                                ipstat.ips_cantforward++;
                                m_freem(m);
                                return;
                        }

                        /*
                         * The process-level routing daemon needs to receive
                         * all multicast IGMP packets, whether or not this
                         * host belongs to their destination groups.
                         */
                        if (ip->ip_p == IPPROTO_IGMP)
                                goto ours;
                        ipstat.ips_forward++;
                }
                /*
                 * See if we belong to the destination multicast group on the
                 * arrival interface.
                 */
                IN_LOOKUP_MULTI(ip->ip_dst, m->m_pkthdr.rcvif, inm);
                if (inm == NULL) {
                        ipstat.ips_notmember++;
                        m_freem(m);
                        return;
                }
                goto ours;
        }
        if (ip->ip_dst.s_addr == INADDR_BROADCAST)
                goto ours;
        if (ip->ip_dst.s_addr == INADDR_ANY)
                goto ours;

        /*
         * FAITH(Firewall Aided Internet Translator)
         */
        if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
                if (ip_keepfaith) {
                        if (ip->ip_p == IPPROTO_TCP || ip->ip_p == IPPROTO_ICMP)
                                goto ours;
                }
                m_freem(m);
                return;
        }

        /*
         * Not for us; forward if possible and desirable.
         */
        if (!ipforwarding) {
                ipstat.ips_cantforward++;
                m_freem(m);
        } else {
#ifdef IPSEC
                /*
                 * Enforce inbound IPsec SPD.
                 */
                if (ipsec4_in_reject(m, NULL)) {
                        ipsecstat.in_polvio++;
                        goto bad;
                }
#endif
#ifdef FAST_IPSEC
                mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
                crit_enter();
                if (mtag != NULL) {
                        tdbi = (struct tdb_ident *)m_tag_data(mtag);
                        sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
                } else {
                        sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
                                                   IP_FORWARDING, &error);
                }
                if (sp == NULL) {       /* NB: can happen if error */
                        crit_exit();
                        /*XXX error stat???*/
                        DPRINTF(("ip_input: no SP for forwarding\n"));  /*XXX*/
                        goto bad;
                }

                /*
                 * Check security policy against packet attributes.
                 */
                error = ipsec_in_reject(sp, m);
                KEY_FREESP(&sp);
                crit_exit();
                if (error) {
                        ipstat.ips_cantforward++;
                        goto bad;
                }
#endif
                ip_forward(m, using_srcrt, next_hop);
        }
        return;

ours:

        /*
         * IPSTEALTH: Process non-routing options only
         * if the packet is destined for us.
         */
        if (ipstealth &&
            hlen > sizeof(struct ip) &&
            ip_dooptions(m, 1, next_hop))
                return;

        /* Count the packet in the ip address stats */
        if (ia != NULL) {
                ia->ia_ifa.if_ipackets++;
                ia->ia_ifa.if_ibytes += m->m_pkthdr.len;
        }

        /*
         * If offset or IP_MF are set, must reassemble.
         * Otherwise, nothing need be done.
         * (We could look in the reassembly queue to see
         * if the packet was previously fragmented,
         * but it's not worth the time; just let them time out.)
         */
        if (ip->ip_off & (IP_MF | IP_OFFMASK)) {
                /*
                 * Attempt reassembly; if it succeeds, proceed.
                 * ip_reass() will return a different mbuf, and update
                 * the divert info in divert_info.
                 */
                m = ip_reass(m, &divert_info);
                if (m == NULL)
                        return;

                needredispatch = TRUE;
                ip = mtod(m, struct ip *);
                /* Get the header length of the reassembled packet */
                hlen = IP_VHL_HL(ip->ip_vhl) << 2;
#ifdef IPDIVERT
                /* Restore original checksum before diverting packet */
                if (divert_info != 0) {
                        ip->ip_len += hlen;
                        ip->ip_len = htons(ip->ip_len);
                        ip->ip_off = htons(ip->ip_off);
                        ip->ip_sum = 0;
                        if (hlen == sizeof(struct ip))
                                ip->ip_sum = in_cksum_hdr(ip);
                        else
                                ip->ip_sum = in_cksum(m, hlen);
                        ip->ip_off = ntohs(ip->ip_off);
                        ip->ip_len = ntohs(ip->ip_len);
                        ip->ip_len -= hlen;
                }
#endif
        } else {
                ip->ip_len -= hlen;
        }

#ifdef IPDIVERT
        /*
         * Divert or tee packet to the divert protocol if required.
         */
        if (divert_info != 0) {
                struct mbuf *clone = NULL;

                /* Clone packet if we're doing a 'tee' */
                if ((divert_info & IP_FW_PORT_TEE_FLAG) != 0)
                        clone = m_dup(m, MB_DONTWAIT);

                /* Restore packet header fields to original values */
                ip->ip_len += hlen;
                ip->ip_len = htons(ip->ip_len);
                ip->ip_off = htons(ip->ip_off);

                /* Deliver packet to divert input routine */
                divert_packet(m, 1, divert_info & 0xffff);
                ipstat.ips_delivered++;

                /* If 'tee', continue with original packet */
                if (clone == NULL)
                        return;
                m = clone;
                ip = mtod(m, struct ip *);
                ip->ip_len += hlen;
                /*
                 * Jump backwards to complete processing of the
                 * packet. But first clear divert_info to avoid
                 * entering this block again.
                 * We do not need to clear args.divert_rule as
                 * it will not be used.
                 *
                 * XXX Better safe than sorry, remove the DIVERT tag.
                 */
                mtag = m_tag_find(m, PACKET_TAG_IPFW_DIVERT, NULL);
                if (mtag != NULL)
                        m_tag_delete(m, mtag);
                
                divert_info = 0;
                goto pass;
        }
#endif

#ifdef IPSEC
        /*
         * enforce IPsec policy checking if we are seeing last header.
         * note that we do not visit this with protocols with pcb layer
         * code - like udp/tcp/raw ip.
         */
        if ((inetsw[ip_protox[ip->ip_p]].pr_flags & PR_LASTHDR) &&
            ipsec4_in_reject(m, NULL)) {
                ipsecstat.in_polvio++;
                goto bad;
        }
#endif
#if FAST_IPSEC
        /*
         * enforce IPsec policy checking if we are seeing last header.
         * note that we do not visit this with protocols with pcb layer
         * code - like udp/tcp/raw ip.
         */
        if (inetsw[ip_protox[ip->ip_p]].pr_flags & PR_LASTHDR) {
                /*
                 * Check if the packet has already had IPsec processing
                 * done.  If so, then just pass it along.  This tag gets
                 * set during AH, ESP, etc. input handling, before the
                 * packet is returned to the ip input queue for delivery.
                 */
                mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
                crit_enter();
                if (mtag != NULL) {
                        tdbi = (struct tdb_ident *)m_tag_data(mtag);
                        sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
                } else {
                        sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
                                                   IP_FORWARDING, &error);
                }
                if (sp != NULL) {
                        /*
                         * Check security policy against packet attributes.
                         */
                        error = ipsec_in_reject(sp, m);
                        KEY_FREESP(&sp);
                } else {
                        /* XXX error stat??? */
                        error = EINVAL;
DPRINTF(("ip_input: no SP, packet discarded\n"));/*XXX*/
                        goto bad;
                }
                crit_exit();
                if (error)
                        goto bad;
        }
#endif /* FAST_IPSEC */

        ipstat.ips_delivered++;
        if (needredispatch) {
                struct netmsg_packet *pmsg;
                lwkt_port_t port;

                ip->ip_off = htons(ip->ip_off);
                ip->ip_len = htons(ip->ip_len);
                port = ip_mport_in(&m);
                if (port == NULL)
                        return;

                pmsg = &m->m_hdr.mh_netmsg;
                netmsg_init(&pmsg->nm_netmsg, &netisr_apanic_rport, 0,
                            transport_processing_handler);
                pmsg->nm_packet = m;
                pmsg->nm_netmsg.nm_lmsg.u.ms_result = hlen;

                ip = mtod(m, struct ip *);
                ip->ip_len = ntohs(ip->ip_len);
                ip->ip_off = ntohs(ip->ip_off);
                lwkt_sendmsg(port, &pmsg->nm_netmsg.nm_lmsg);
        } else {
                transport_processing_oncpu(m, hlen, ip);
        }
        return;

bad:
        m_freem(m);
}

/*
 * Take incoming datagram fragment and try to reassemble it into
 * whole datagram.  If a chain for reassembly of this datagram already
 * exists, then it is given as fp; otherwise have to make a chain.
 *
 * When IPDIVERT enabled, keep additional state with each packet that
 * tells us if we need to divert or tee the packet we're building.
 * In particular, *divinfo includes the port and TEE flag.
 */

static struct mbuf *
ip_reass(struct mbuf *m, u_int32_t *divinfo)
{
        struct ip *ip = mtod(m, struct ip *);
        struct mbuf *p = NULL, *q, *nq;
        struct mbuf *n;
        struct ipq *fp = NULL;
        int hlen = IP_VHL_HL(ip->ip_vhl) << 2;
        int i, next;
        u_short sum;
#ifdef IPDIVERT
        struct m_tag *mtag;
#endif

        /* If maxnipq is 0, never accept fragments. */
        if (maxnipq == 0) {
                ipstat.ips_fragments++;
                ipstat.ips_fragdropped++;
                m_freem(m);
                return NULL;
        }

        sum = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
        /*
         * Look for queue of fragments of this datagram.
         */
        for (fp = ipq[sum].next; fp != &ipq[sum]; fp = fp->next)
                if (ip->ip_id == fp->ipq_id &&
                    ip->ip_src.s_addr == fp->ipq_src.s_addr &&
                    ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
                    ip->ip_p == fp->ipq_p)
                        goto found;

        fp = NULL;

        /*
         * Enforce upper bound on number of fragmented packets
         * for which we attempt reassembly;
         * If maxnipq is -1, accept all fragments without limitation.
         */
        if (nipq > maxnipq && maxnipq > 0) {
                /*
                 * drop something from the tail of the current queue
                 * before proceeding further
                 */
                if (ipq[sum].prev == &ipq[sum]) {   /* gak */
                        for (i = 0; i < IPREASS_NHASH; i++) {
                                if (ipq[i].prev != &ipq[i]) {
                                        ipstat.ips_fragtimeout +=
                                            ipq[i].prev->ipq_nfrags;
                                        ip_freef(ipq[i].prev);
                                        break;
                                }
                        }
                } else {
                        ipstat.ips_fragtimeout +=
                            ipq[sum].prev->ipq_nfrags;
                        ip_freef(ipq[sum].prev);
                }
        }
found:
        /*
         * Adjust ip_len to not reflect header,
         * convert offset of this to bytes.
         */
        ip->ip_len -= hlen;
        if (ip->ip_off & IP_MF) {
                /*
                 * Make sure that fragments have a data length
                 * that's a non-zero multiple of 8 bytes.
                 */
                if (ip->ip_len == 0 || (ip->ip_len & 0x7) != 0) {
                        ipstat.ips_toosmall++; /* XXX */
                        m_freem(m);
                        return NULL;
                }
                m->m_flags |= M_FRAG;
        } else
                m->m_flags &= ~M_FRAG;
        ip->ip_off <<= 3;

        ipstat.ips_fragments++;
        m->m_pkthdr.header = ip;

        /*
         * If the hardware has not done csum over this fragment
         * then csum_data is not valid at all.
         */
        if ((m->m_pkthdr.csum_flags & (CSUM_FRAG_NOT_CHECKED | CSUM_DATA_VALID))
            == (CSUM_FRAG_NOT_CHECKED | CSUM_DATA_VALID)) {
                m->m_pkthdr.csum_data = 0;
                m->m_pkthdr.csum_flags &= ~(CSUM_DATA_VALID | CSUM_PSEUDO_HDR);
        }

        /*
         * Presence of header sizes in mbufs
         * would confuse code below.
         */
        m->m_data += hlen;
        m->m_len -= hlen;

        /*
         * If first fragment to arrive, create a reassembly queue.
         */
        if (fp == NULL) {
                if ((fp = mpipe_alloc_nowait(&ipq_mpipe)) == NULL)
                        goto dropfrag;
                insque(fp, &ipq[sum]);
                nipq++;
                fp->ipq_nfrags = 1;
                fp->ipq_ttl = IPFRAGTTL;
                fp->ipq_p = ip->ip_p;
                fp->ipq_id = ip->ip_id;
                fp->ipq_src = ip->ip_src;
                fp->ipq_dst = ip->ip_dst;
                fp->ipq_frags = m;
                m->m_nextpkt = NULL;
#ifdef IPDIVERT
                fp->ipq_div_info = 0;
#endif
                goto inserted;
        } else {
                fp->ipq_nfrags++;
        }

#define GETIP(m)        ((struct ip*)((m)->m_pkthdr.header))

        /*
         * Find a segment which begins after this one does.
         */
        for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
                if (GETIP(q)->ip_off > ip->ip_off)
                        break;

        /*
         * If there is a preceding segment, it may provide some of
         * our data already.  If so, drop the data from the incoming
         * segment.  If it provides all of our data, drop us, otherwise
         * stick new segment in the proper place.
         *
         * If some of the data is dropped from the the preceding
         * segment, then it's checksum is invalidated.
         */
        if (p) {
                i = GETIP(p)->ip_off + GETIP(p)->ip_len - ip->ip_off;
                if (i > 0) {
                        if (i >= ip->ip_len)
                                goto dropfrag;
                        m_adj(m, i);
                        m->m_pkthdr.csum_flags = 0;
                        ip->ip_off += i;
                        ip->ip_len -= i;
                }
                m->m_nextpkt = p->m_nextpkt;
                p->m_nextpkt = m;
        } else {
                m->m_nextpkt = fp->ipq_frags;
                fp->ipq_frags = m;
        }

        /*
         * While we overlap succeeding segments trim them or,
         * if they are completely covered, dequeue them.
         */
        for (; q != NULL && ip->ip_off + ip->ip_len > GETIP(q)->ip_off;
             q = nq) {
                i = (ip->ip_off + ip->ip_len) - GETIP(q)->ip_off;
                if (i < GETIP(q)->ip_len) {
                        GETIP(q)->ip_len -= i;
                        GETIP(q)->ip_off += i;
                        m_adj(q, i);
                        q->m_pkthdr.csum_flags = 0;
                        break;
                }
                nq = q->m_nextpkt;
                m->m_nextpkt = nq;
                ipstat.ips_fragdropped++;
                fp->ipq_nfrags--;
                q->m_nextpkt = NULL;
                m_freem(q);
        }

inserted:

#ifdef IPDIVERT
        /*
         * Transfer firewall instructions to the fragment structure.
         * Only trust info in the fragment at offset 0.
         */
        if (ip->ip_off == 0) {
                fp->ipq_div_info = *divinfo;
        } else {
                mtag = m_tag_find(m, PACKET_TAG_IPFW_DIVERT, NULL);
                if (mtag != NULL)
                        m_tag_delete(m, mtag);
        }
        *divinfo = 0;
#endif

        /*
         * Check for complete reassembly and perform frag per packet
         * limiting.
         *
         * Frag limiting is performed here so that the nth frag has
         * a chance to complete the packet before we drop the packet.
         * As a result, n+1 frags are actually allowed per packet, but
         * only n will ever be stored. (n = maxfragsperpacket.)
         *
         */
        next = 0;
        for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
                if (GETIP(q)->ip_off != next) {
                        if (fp->ipq_nfrags > maxfragsperpacket) {
                                ipstat.ips_fragdropped += fp->ipq_nfrags;
                                ip_freef(fp);
                        }
                        return (NULL);
                }
                next += GETIP(q)->ip_len;
        }
        /* Make sure the last packet didn't have the IP_MF flag */
        if (p->m_flags & M_FRAG) {
                if (fp->ipq_nfrags > maxfragsperpacket) {
                        ipstat.ips_fragdropped += fp->ipq_nfrags;
                        ip_freef(fp);
                }
                return (NULL);
        }

        /*
         * Reassembly is complete.  Make sure the packet is a sane size.
         */
        q = fp->ipq_frags;
        ip = GETIP(q);
        if (next + (IP_VHL_HL(ip->ip_vhl) << 2) > IP_MAXPACKET) {
                ipstat.ips_toolong++;
                ipstat.ips_fragdropped += fp->ipq_nfrags;
                ip_freef(fp);
                return (NULL);
        }

        /*
         * Concatenate fragments.
         */
        m = q;
        n = m->m_next;
        m->m_next = NULL;
        m_cat(m, n);
        nq = q->m_nextpkt;
        q->m_nextpkt = NULL;
        for (q = nq; q != NULL; q = nq) {
                nq = q->m_nextpkt;
                q->m_nextpkt = NULL;
                m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
                m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
                m_cat(m, q);
        }

        /*
         * Clean up the 1's complement checksum.  Carry over 16 bits must
         * be added back.  This assumes no more then 65535 packet fragments
         * were reassembled.  A second carry can also occur (but not a third).
         */
        m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
                                (m->m_pkthdr.csum_data >> 16);
        if (m->m_pkthdr.csum_data > 0xFFFF)
                m->m_pkthdr.csum_data -= 0xFFFF;


#ifdef IPDIVERT
        /*
         * Extract firewall instructions from the fragment structure.
         */
        *divinfo = fp->ipq_div_info;
#endif

        /*
         * Create header for new ip packet by
         * modifying header of first packet;
         * dequeue and discard fragment reassembly header.
         * Make header visible.
         */
        ip->ip_len = next;
        ip->ip_src = fp->ipq_src;
        ip->ip_dst = fp->ipq_dst;
        remque(fp);
        nipq--;
        mpipe_free(&ipq_mpipe, fp);
        m->m_len += (IP_VHL_HL(ip->ip_vhl) << 2);
        m->m_data -= (IP_VHL_HL(ip->ip_vhl) << 2);
        /* some debugging cruft by sklower, below, will go away soon */
        if (m->m_flags & M_PKTHDR) { /* XXX this should be done elsewhere */
                int plen = 0;

                for (n = m; n; n = n->m_next)
                        plen += n->m_len;
                m->m_pkthdr.len = plen;
        }

        ipstat.ips_reassembled++;
        return (m);

dropfrag:
#ifdef IPDIVERT
        *divinfo = 0;
#endif
        ipstat.ips_fragdropped++;
        if (fp != NULL)
                fp->ipq_nfrags--;
        m_freem(m);
        return (NULL);

#undef GETIP
}

/*
 * Free a fragment reassembly header and all
 * associated datagrams.
 */
static void
ip_freef(struct ipq *fp)
{
        struct mbuf *q;

        while (fp->ipq_frags) {
                q = fp->ipq_frags;
                fp->ipq_frags = q->m_nextpkt;
                q->m_nextpkt = NULL;
                m_freem(q);
        }
        remque(fp);
        mpipe_free(&ipq_mpipe, fp);
        nipq--;
}

/*
 * IP timer processing;
 * if a timer expires on a reassembly
 * queue, discard it.
 */
void
ip_slowtimo(void)
{
        struct ipq *fp;
        int i;

        crit_enter();
        for (i = 0; i < IPREASS_NHASH; i++) {
                fp = ipq[i].next;
                if (fp == NULL)
                        continue;
                while (fp != &ipq[i]) {
                        --fp->ipq_ttl;
                        fp = fp->next;
                        if (fp->prev->ipq_ttl == 0) {
                                ipstat.ips_fragtimeout += fp->prev->ipq_nfrags;
                                ip_freef(fp->prev);
                        }
                }
        }
        /*
         * If we are over the maximum number of fragments
         * (due to the limit being lowered), drain off
         * enough to get down to the new limit.
         */
        if (maxnipq >= 0 && nipq > maxnipq) {
                for (i = 0; i < IPREASS_NHASH; i++) {
                        while (nipq > maxnipq &&
                                (ipq[i].next != &ipq[i])) {
                                ipstat.ips_fragdropped +=
                                    ipq[i].next->ipq_nfrags;
                                ip_freef(ipq[i].next);
                        }
                }
        }
        ipflow_slowtimo();
        crit_exit();
}

/*
 * Drain off all datagram fragments.
 */
void
ip_drain(void)
{
        int i;

        for (i = 0; i < IPREASS_NHASH; i++) {
                while (ipq[i].next != &ipq[i]) {
                        ipstat.ips_fragdropped += ipq[i].next->ipq_nfrags;
                        ip_freef(ipq[i].next);
                }
        }
        in_rtqdrain();
}

/*
 * Do option processing on a datagram,
 * possibly discarding it if bad options are encountered,
 * or forwarding it if source-routed.
 * The pass argument is used when operating in the IPSTEALTH
 * mode to tell what options to process:
 * [LS]SRR (pass 0) or the others (pass 1).
 * The reason for as many as two passes is that when doing IPSTEALTH,
 * non-routing options should be processed only if the packet is for us.
 * Returns 1 if packet has been forwarded/freed,
 * 0 if the packet should be processed further.
 */
static int
ip_dooptions(struct mbuf *m, int pass, struct sockaddr_in *next_hop)
{
        struct sockaddr_in ipaddr = { sizeof ipaddr, AF_INET };
        struct ip *ip = mtod(m, struct ip *);
        u_char *cp;
        struct in_ifaddr *ia;
        int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB;
        boolean_t forward = FALSE;
        struct in_addr *sin, dst;
        n_time ntime;

        dst = ip->ip_dst;
        cp = (u_char *)(ip + 1);
        cnt = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof(struct ip);
        for (; cnt > 0; cnt -= optlen, cp += optlen) {
                opt = cp[IPOPT_OPTVAL];
                if (opt == IPOPT_EOL)
                        break;
                if (opt == IPOPT_NOP)
                        optlen = 1;
                else {
                        if (cnt < IPOPT_OLEN + sizeof(*cp)) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                        optlen = cp[IPOPT_OLEN];
                        if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                }
                switch (opt) {

                default:
                        break;

                /*
                 * Source routing with record.
                 * Find interface with current destination address.
                 * If none on this machine then drop if strictly routed,
                 * or do nothing if loosely routed.
                 * Record interface address and bring up next address
                 * component.  If strictly routed make sure next
                 * address is on directly accessible net.
                 */
                case IPOPT_LSRR:
                case IPOPT_SSRR:
                        if (ipstealth && pass > 0)
                                break;
                        if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                        if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        ipaddr.sin_addr = ip->ip_dst;
                        ia = (struct in_ifaddr *)
                                ifa_ifwithaddr((struct sockaddr *)&ipaddr);
                        if (ia == NULL) {
                                if (opt == IPOPT_SSRR) {
                                        type = ICMP_UNREACH;
                                        code = ICMP_UNREACH_SRCFAIL;
                                        goto bad;
                                }
                                if (!ip_dosourceroute)
                                        goto nosourcerouting;
                                /*
                                 * Loose routing, and not at next destination
                                 * yet; nothing to do except forward.
                                 */
                                break;
                        }
                        off--;                  /* 0 origin */
                        if (off > optlen - (int)sizeof(struct in_addr)) {
                                /*
                                 * End of source route.  Should be for us.
                                 */
                                if (!ip_acceptsourceroute)
                                        goto nosourcerouting;
                                save_rte(cp, ip->ip_src);
                                break;
                        }
                        if (ipstealth)
                                goto dropit;
                        if (!ip_dosourceroute) {
                                if (ipforwarding) {
                                        char buf[sizeof "aaa.bbb.ccc.ddd"];

                                        /*
                                         * Acting as a router, so generate ICMP
                                         */
nosourcerouting:
                                        strcpy(buf, inet_ntoa(ip->ip_dst));
                                        log(LOG_WARNING,
                                            "attempted source route from %s to %s\n",
                                            inet_ntoa(ip->ip_src), buf);
                                        type = ICMP_UNREACH;
                                        code = ICMP_UNREACH_SRCFAIL;
                                        goto bad;
                                } else {
                                        /*
                                         * Not acting as a router,
                                         * so silently drop.
                                         */
dropit:
                                        ipstat.ips_cantforward++;
                                        m_freem(m);
                                        return (1);
                                }
                        }

                        /*
                         * locate outgoing interface
                         */
                        memcpy(&ipaddr.sin_addr, cp + off,
                            sizeof ipaddr.sin_addr);

                        if (opt == IPOPT_SSRR) {
#define INA     struct in_ifaddr *
#define SA      struct sockaddr *
                                if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr))
                                                                        == NULL)
                                        ia = (INA)ifa_ifwithnet((SA)&ipaddr);
                        } else
                                ia = ip_rtaddr(ipaddr.sin_addr,
                                               &ipforward_rt[mycpuid]);
                        if (ia == NULL) {
                                type = ICMP_UNREACH;
                                code = ICMP_UNREACH_SRCFAIL;
                                goto bad;
                        }
                        ip->ip_dst = ipaddr.sin_addr;
                        memcpy(cp + off, &IA_SIN(ia)->sin_addr,
                            sizeof(struct in_addr));
                        cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                        /*
                         * Let ip_intr's mcast routing check handle mcast pkts
                         */
                        forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
                        break;

                case IPOPT_RR:
                        if (ipstealth && pass == 0)
                                break;
                        if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        /*
                         * If no space remains, ignore.
                         */
                        off--;                  /* 0 origin */
                        if (off > optlen - (int)sizeof(struct in_addr))
                                break;
                        memcpy(&ipaddr.sin_addr, &ip->ip_dst,
                            sizeof ipaddr.sin_addr);
                        /*
                         * locate outgoing interface; if we're the destination,
                         * use the incoming interface (should be same).
                         */
                        if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
                            (ia = ip_rtaddr(ipaddr.sin_addr,
                                            &ipforward_rt[mycpuid]))
                                                                     == NULL) {
                                type = ICMP_UNREACH;
                                code = ICMP_UNREACH_HOST;
                                goto bad;
                        }
                        memcpy(cp + off, &IA_SIN(ia)->sin_addr,
                            sizeof(struct in_addr));
                        cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                        break;

                case IPOPT_TS:
                        if (ipstealth && pass == 0)
                                break;
                        code = cp - (u_char *)ip;
                        if (optlen < 4 || optlen > 40) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                        if ((off = cp[IPOPT_OFFSET]) < 5) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                        if (off > optlen - (int)sizeof(int32_t)) {
                                cp[IPOPT_OFFSET + 1] += (1 << 4);
                                if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
                                        code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                        goto bad;
                                }
                                break;
                        }
                        off--;                          /* 0 origin */
                        sin = (struct in_addr *)(cp + off);
                        switch (cp[IPOPT_OFFSET + 1] & 0x0f) {

                        case IPOPT_TS_TSONLY:
                                break;

                        case IPOPT_TS_TSANDADDR:
                                if (off + sizeof(n_time) +
                                    sizeof(struct in_addr) > optlen) {
                                        code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                        goto bad;
                                }
                                ipaddr.sin_addr = dst;
                                ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
                                                            m->m_pkthdr.rcvif);
                                if (ia == NULL)
                                        continue;
                                memcpy(sin, &IA_SIN(ia)->sin_addr,
                                    sizeof(struct in_addr));
                                cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                                off += sizeof(struct in_addr);
                                break;

                        case IPOPT_TS_PRESPEC:
                                if (off + sizeof(n_time) +
                                    sizeof(struct in_addr) > optlen) {
                                        code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                        goto bad;
                                }
                                memcpy(&ipaddr.sin_addr, sin,
                                    sizeof(struct in_addr));
                                if (ifa_ifwithaddr((SA)&ipaddr) == NULL)
                                        continue;
                                cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                                off += sizeof(struct in_addr);
                                break;

                        default:
                                code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
                                goto bad;
                        }
                        ntime = iptime();
                        memcpy(cp + off, &ntime, sizeof(n_time));
                        cp[IPOPT_OFFSET] += sizeof(n_time);
                }
        }
        if (forward && ipforwarding) {
                ip_forward(m, TRUE, next_hop);
                return (1);
        }
        return (0);
bad:
        icmp_error(m, type, code, 0, 0);
        ipstat.ips_badoptions++;
        return (1);
}

/*
 * Given address of next destination (final or next hop),
 * return internet address info of interface to be used to get there.
 */
struct in_ifaddr *
ip_rtaddr(struct in_addr dst, struct route *ro)
{
        struct sockaddr_in *sin;

        sin = (struct sockaddr_in *)&ro->ro_dst;

        if (ro->ro_rt == NULL || dst.s_addr != sin->sin_addr.s_addr) {
                if (ro->ro_rt != NULL) {
                        RTFREE(ro->ro_rt);
                        ro->ro_rt = NULL;
                }
                sin->sin_family = AF_INET;
                sin->sin_len = sizeof *sin;
                sin->sin_addr = dst;
                rtalloc_ign(ro, RTF_PRCLONING);
        }

        if (ro->ro_rt == NULL)
                return (NULL);

        return (ifatoia(ro->ro_rt->rt_ifa));
}

/*
 * Save incoming source route for use in replies,
 * to be picked up later by ip_srcroute if the receiver is interested.
 */
void
save_rte(u_char *option, struct in_addr dst)
{
        unsigned olen;

        olen = option[IPOPT_OLEN];
#ifdef DIAGNOSTIC
        if (ipprintfs)
                kprintf("save_rte: olen %d\n", olen);
#endif
        if (olen > sizeof(ip_srcrt) - (1 + sizeof(dst)))
                return;
        bcopy(option, ip_srcrt.srcopt, olen);
        ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
        ip_srcrt.dst = dst;
}

/*
 * Retrieve incoming source route for use in replies,
 * in the same form used by setsockopt.
 * The first hop is placed before the options, will be removed later.
 */
struct mbuf *
ip_srcroute(void)
{
        struct in_addr *p, *q;
        struct mbuf *m;

        if (ip_nhops == 0)
                return (NULL);
        m = m_get(MB_DONTWAIT, MT_HEADER);
        if (m == NULL)
                return (NULL);

#define OPTSIZ  (sizeof(ip_srcrt.nop) + sizeof(ip_srcrt.srcopt))

        /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
        m->m_len = ip_nhops * sizeof(struct in_addr) + sizeof(struct in_addr) +
            OPTSIZ;
#ifdef DIAGNOSTIC
        if (ipprintfs)
                kprintf("ip_srcroute: nhops %d mlen %d", ip_nhops, m->m_len);
#endif

        /*
         * First save first hop for return route
         */
        p = &ip_srcrt.route[ip_nhops - 1];
        *(mtod(m, struct in_addr *)) = *p--;
#ifdef DIAGNOSTIC
        if (ipprintfs)
                kprintf(" hops %x", ntohl(mtod(m, struct in_addr *)->s_addr));
#endif

        /*
         * Copy option fields and padding (nop) to mbuf.
         */
        ip_srcrt.nop = IPOPT_NOP;
        ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
        memcpy(mtod(m, caddr_t) + sizeof(struct in_addr), &ip_srcrt.nop,
            OPTSIZ);
        q = (struct in_addr *)(mtod(m, caddr_t) +
            sizeof(struct in_addr) + OPTSIZ);
#undef OPTSIZ
        /*
         * Record return path as an IP source route,
         * reversing the path (pointers are now aligned).
         */
        while (p >= ip_srcrt.route) {
#ifdef DIAGNOSTIC
                if (ipprintfs)
                        kprintf(" %x", ntohl(q->s_addr));
#endif
                *q++ = *p--;
        }
        /*
         * Last hop goes to final destination.
         */
        *q = ip_srcrt.dst;
#ifdef DIAGNOSTIC
        if (ipprintfs)
                kprintf(" %x\n", ntohl(q->s_addr));
#endif
        return (m);
}

/*
 * Strip out IP options.
 */
void
ip_stripoptions(struct mbuf *m)
{
        int datalen;
        struct ip *ip = mtod(m, struct ip *);
        caddr_t opts;
        int optlen;

        optlen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof(struct ip);
        opts = (caddr_t)(ip + 1);
        datalen = m->m_len - (sizeof(struct ip) + optlen);
        bcopy(opts + optlen, opts, datalen);
        m->m_len -= optlen;
        if (m->m_flags & M_PKTHDR)
                m->m_pkthdr.len -= optlen;
        ip->ip_vhl = IP_MAKE_VHL(IPVERSION, sizeof(struct ip) >> 2);
}

u_char inetctlerrmap[PRC_NCMDS] = {
        0,              0,              0,              0,
        0,              EMSGSIZE,       EHOSTDOWN,      EHOSTUNREACH,
        EHOSTUNREACH,   EHOSTUNREACH,   ECONNREFUSED,   ECONNREFUSED,
        EMSGSIZE,       EHOSTUNREACH,   0,              0,
        0,              0,              0,              0,
        ENOPROTOOPT,    ECONNREFUSED
};

/*
 * Forward a packet.  If some error occurs return the sender
 * an icmp packet.  Note we can't always generate a meaningful
 * icmp message because icmp doesn't have a large enough repertoire
 * of codes and types.
 *
 * If not forwarding, just drop the packet.  This could be confusing
 * if ipforwarding was zero but some routing protocol was advancing
 * us as a gateway to somewhere.  However, we must let the routing
 * protocol deal with that.
 *
 * The using_srcrt parameter indicates whether the packet is being forwarded
 * via a source route.
 */
void
ip_forward(struct mbuf *m, boolean_t using_srcrt, struct sockaddr_in *next_hop)
{
        struct ip *ip = mtod(m, struct ip *);
        struct sockaddr_in *ipforward_rtaddr;
        struct rtentry *rt;
        int error, type = 0, code = 0, destmtu = 0;
        struct mbuf *mcopy;
        n_long dest;
        struct in_addr pkt_dst;
        struct route *cache_rt = &ipforward_rt[mycpuid];

        dest = INADDR_ANY;
        /*
         * Cache the destination address of the packet; this may be
         * changed by use of 'ipfw fwd'.
         */
        pkt_dst = (next_hop != NULL) ? next_hop->sin_addr : ip->ip_dst;

#ifdef DIAGNOSTIC
        if (ipprintfs)
                kprintf("forward: src %x dst %x ttl %x\n",
                       ip->ip_src.s_addr, pkt_dst.s_addr, ip->ip_ttl);
#endif

        if (m->m_flags & (M_BCAST | M_MCAST) || !in_canforward(pkt_dst)) {
                ipstat.ips_cantforward++;
                m_freem(m);
                return;
        }
        if (!ipstealth && ip->ip_ttl <= IPTTLDEC) {
                icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, dest, 0);
                return;
        }

        ipforward_rtaddr = (struct sockaddr_in *) &cache_rt->ro_dst;
        if (cache_rt->ro_rt == NULL ||
            ipforward_rtaddr->sin_addr.s_addr != pkt_dst.s_addr) {
                if (cache_rt->ro_rt != NULL) {
                        RTFREE(cache_rt->ro_rt);
                        cache_rt->ro_rt = NULL;
                }
                ipforward_rtaddr->sin_family = AF_INET;
                ipforward_rtaddr->sin_len = sizeof(struct sockaddr_in);
                ipforward_rtaddr->sin_addr = pkt_dst;
                rtalloc_ign(cache_rt, RTF_PRCLONING);
                if (cache_rt->ro_rt == NULL) {
                        icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, dest, 0);
                        return;
                }
        }
        rt = cache_rt->ro_rt;

        /*
         * Save the IP header and at most 8 bytes of the payload,
         * in case we need to generate an ICMP message to the src.
         *
         * XXX this can be optimized a lot by saving the data in a local
         * buffer on the stack (72 bytes at most), and only allocating the
         * mbuf if really necessary. The vast majority of the packets
         * are forwarded without having to send an ICMP back (either
         * because unnecessary, or because rate limited), so we are
         * really we are wasting a lot of work here.
         *
         * We don't use m_copy() because it might return a reference
         * to a shared cluster. Both this function and ip_output()
         * assume exclusive access to the IP header in `m', so any
         * data in a cluster may change before we reach icmp_error().
         */
        MGETHDR(mcopy, MB_DONTWAIT, m->m_type);
        if (mcopy != NULL && !m_dup_pkthdr(mcopy, m, MB_DONTWAIT)) {
                /*
                 * It's probably ok if the pkthdr dup fails (because
                 * the deep copy of the tag chain failed), but for now
                 * be conservative and just discard the copy since
                 * code below may some day want the tags.
                 */
                m_free(mcopy);
                mcopy = NULL;
        }
        if (mcopy != NULL) {
                mcopy->m_len = imin((IP_VHL_HL(ip->ip_vhl) << 2) + 8,
                    (int)ip->ip_len);
                mcopy->m_pkthdr.len = mcopy->m_len;
                m_copydata(m, 0, mcopy->m_len, mtod(mcopy, caddr_t));
        }

        if (!ipstealth)
                ip->ip_ttl -= IPTTLDEC;

        /*
         * If forwarding packet using same interface that it came in on,
         * perhaps should send a redirect to sender to shortcut a hop.
         * Only send redirect if source is sending directly to us,
         * and if packet was not source routed (or has any options).
         * Also, don't send redirect if forwarding using a default route
         * or a route modified by a redirect.
         */
        if (rt->rt_ifp == m->m_pkthdr.rcvif &&
            !(rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) &&
            satosin(rt_key(rt))->sin_addr.s_addr != INADDR_ANY &&
            ipsendredirects && !using_srcrt && next_hop == NULL) {
                u_long src = ntohl(ip->ip_src.s_addr);
                struct in_ifaddr *rt_ifa = (struct in_ifaddr *)rt->rt_ifa;

                if (rt_ifa != NULL &&
                    (src & rt_ifa->ia_subnetmask) == rt_ifa->ia_subnet) {
                        if (rt->rt_flags & RTF_GATEWAY)
                                dest = satosin(rt->rt_gateway)->sin_addr.s_addr;
                        else
                                dest = pkt_dst.s_addr;
                        /*
                         * Router requirements says to only send
                         * host redirects.
                         */
                        type = ICMP_REDIRECT;
                        code = ICMP_REDIRECT_HOST;
#ifdef DIAGNOSTIC
                        if (ipprintfs)
                                kprintf("redirect (%d) to %x\n", code, dest);
#endif
                }
        }

        error = ip_output(m, NULL, cache_rt, IP_FORWARDING, NULL, NULL);
        if (error == 0) {
                ipstat.ips_forward++;
                if (type == 0) {
                        if (mcopy) {
                                ipflow_create(cache_rt, mcopy);
                                m_freem(mcopy);
                        }
                        return;         /* most common case */
                } else {
                        ipstat.ips_redirectsent++;
                }
        } else {
                ipstat.ips_cantforward++;
        }

        if (mcopy == NULL)
                return;

        /*
         * Send ICMP message.
         */

        switch (error) {

        case 0:                         /* forwarded, but need redirect */
                /* type, code set above */
                break;

        case ENETUNREACH:               /* shouldn't happen, checked above */
        case EHOSTUNREACH:
        case ENETDOWN:
        case EHOSTDOWN:
        default:
                type = ICMP_UNREACH;
                code = ICMP_UNREACH_HOST;
                break;

        case EMSGSIZE:
                type = ICMP_UNREACH;
                code = ICMP_UNREACH_NEEDFRAG;
#ifdef IPSEC
                /*
                 * If the packet is routed over IPsec tunnel, tell the
                 * originator the tunnel MTU.
                 *      tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
                 * XXX quickhack!!!
                 */
                if (cache_rt->ro_rt != NULL) {
                        struct secpolicy *sp = NULL;
                        int ipsecerror;
                        int ipsechdr;
                        struct route *ro;

                        sp = ipsec4_getpolicybyaddr(mcopy,
                                                    IPSEC_DIR_OUTBOUND,
                                                    IP_FORWARDING,
                                                    &ipsecerror);

                        if (sp == NULL)
                                destmtu = cache_rt->ro_rt->rt_ifp->if_mtu;
                        else {
                                /* count IPsec header size */
                                ipsechdr = ipsec4_hdrsiz(mcopy,
                                                         IPSEC_DIR_OUTBOUND,
                                                         NULL);

                                /*
                                 * find the correct route for outer IPv4
                                 * header, compute tunnel MTU.
                                 *
                                 */
                                if (sp->req != NULL && sp->req->sav != NULL &&
                                    sp->req->sav->sah != NULL) {
                                        ro = &sp->req->sav->sah->sa_route;
                                        if (ro->ro_rt != NULL &&
                                            ro->ro_rt->rt_ifp != NULL) {
                                                destmtu =
                                                    ro->ro_rt->rt_ifp->if_mtu;
                                                destmtu -= ipsechdr;
                                        }
                                }

                                key_freesp(sp);
                        }
                }
#elif FAST_IPSEC
                /*
                 * If the packet is routed over IPsec tunnel, tell the
                 * originator the tunnel MTU.
                 *      tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
                 * XXX quickhack!!!
                 */
                if (cache_rt->ro_rt != NULL) {
                        struct secpolicy *sp = NULL;
                        int ipsecerror;
                        int ipsechdr;
                        struct route *ro;

                        sp = ipsec_getpolicybyaddr(mcopy,
                                                   IPSEC_DIR_OUTBOUND,
                                                   IP_FORWARDING,
                                                   &ipsecerror);

                        if (sp == NULL)
                                destmtu = cache_rt->ro_rt->rt_ifp->if_mtu;
                        else {
                                /* count IPsec header size */
                                ipsechdr = ipsec4_hdrsiz(mcopy,
                                                         IPSEC_DIR_OUTBOUND,
                                                         NULL);

                                /*
                                 * find the correct route for outer IPv4
                                 * header, compute tunnel MTU.
                                 */

                                if (sp->req != NULL &&
                                    sp->req->sav != NULL &&
                                    sp->req->sav->sah != NULL) {
                                        ro = &sp->req->sav->sah->sa_route;
                                        if (ro->ro_rt != NULL &&
                                            ro->ro_rt->rt_ifp != NULL) {
                                                destmtu =
                                                    ro->ro_rt->rt_ifp->if_mtu;
                                                destmtu -= ipsechdr;
                                        }
                                }

                                KEY_FREESP(&sp);
                        }
                }
#else /* !IPSEC && !FAST_IPSEC */
                if (cache_rt->ro_rt != NULL)
                        destmtu = cache_rt->ro_rt->rt_ifp->if_mtu;
#endif /*IPSEC*/
                ipstat.ips_cantfrag++;
                break;

        case ENOBUFS:
                /*
                 * A router should not generate ICMP_SOURCEQUENCH as
                 * required in RFC1812 Requirements for IP Version 4 Routers.
                 * Source quench could be a big problem under DoS attacks,
                 * or if the underlying interface is rate-limited.
                 * Those who need source quench packets may re-enable them
                 * via the net.inet.ip.sendsourcequench sysctl.
                 */
                if (!ip_sendsourcequench) {
                        m_freem(mcopy);
                        return;
                } else {
                        type = ICMP_SOURCEQUENCH;
                        code = 0;
                }
                break;

        case EACCES:                    /* ipfw denied packet */
                m_freem(mcopy);
                return;
        }
        icmp_error(mcopy, type, code, dest, destmtu);
}

void
ip_savecontrol(struct inpcb *inp, struct mbuf **mp, struct ip *ip,
               struct mbuf *m)
{
        if (inp->inp_socket->so_options & SO_TIMESTAMP) {
                struct timeval tv;

                microtime(&tv);
                *mp = sbcreatecontrol((caddr_t) &tv, sizeof(tv),
                    SCM_TIMESTAMP, SOL_SOCKET);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
        if (inp->inp_flags & INP_RECVDSTADDR) {
                *mp = sbcreatecontrol((caddr_t) &ip->ip_dst,
                    sizeof(struct in_addr), IP_RECVDSTADDR, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
        if (inp->inp_flags & INP_RECVTTL) {
                *mp = sbcreatecontrol((caddr_t) &ip->ip_ttl,
                    sizeof(u_char), IP_RECVTTL, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
#ifdef notyet
        /* XXX
         * Moving these out of udp_input() made them even more broken
         * than they already were.
         */
        /* options were tossed already */
        if (inp->inp_flags & INP_RECVOPTS) {
                *mp = sbcreatecontrol((caddr_t) opts_deleted_above,
                    sizeof(struct in_addr), IP_RECVOPTS, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
        /* ip_srcroute doesn't do what we want here, need to fix */
        if (inp->inp_flags & INP_RECVRETOPTS) {
                *mp = sbcreatecontrol((caddr_t) ip_srcroute(),
                    sizeof(struct in_addr), IP_RECVRETOPTS, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
#endif
        if (inp->inp_flags & INP_RECVIF) {
                struct ifnet *ifp;
                struct sdlbuf {
                        struct sockaddr_dl sdl;
                        u_char  pad[32];
                } sdlbuf;
                struct sockaddr_dl *sdp;
                struct sockaddr_dl *sdl2 = &sdlbuf.sdl;

                if (((ifp = m->m_pkthdr.rcvif)) &&
                    ((ifp->if_index != 0) && (ifp->if_index <= if_index))) {
                        sdp = IF_LLSOCKADDR(ifp);
                        /*
                         * Change our mind and don't try copy.
                         */
                        if ((sdp->sdl_family != AF_LINK) ||
                            (sdp->sdl_len > sizeof(sdlbuf))) {
                                goto makedummy;
                        }
                        bcopy(sdp, sdl2, sdp->sdl_len);
                } else {
makedummy:
                        sdl2->sdl_len =
                            offsetof(struct sockaddr_dl, sdl_data[0]);
                        sdl2->sdl_family = AF_LINK;
                        sdl2->sdl_index = 0;
                        sdl2->sdl_nlen = sdl2->sdl_alen = sdl2->sdl_slen = 0;
                }
                *mp = sbcreatecontrol((caddr_t) sdl2, sdl2->sdl_len,
                        IP_RECVIF, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
}

/*
 * XXX these routines are called from the upper part of the kernel.
 *
 * They could also be moved to ip_mroute.c, since all the RSVP
 *  handling is done there already.
 */
int
ip_rsvp_init(struct socket *so)
{
        if (so->so_type != SOCK_RAW ||
            so->so_proto->pr_protocol != IPPROTO_RSVP)
                return EOPNOTSUPP;

        if (ip_rsvpd != NULL)
                return EADDRINUSE;

        ip_rsvpd = so;
        /*
         * This may seem silly, but we need to be sure we don't over-increment
         * the RSVP counter, in case something slips up.
         */
        if (!ip_rsvp_on) {
                ip_rsvp_on = 1;
                rsvp_on++;
        }

        return 0;
}

int
ip_rsvp_done(void)
{
        ip_rsvpd = NULL;
        /*
         * This may seem silly, but we need to be sure we don't over-decrement
         * the RSVP counter, in case something slips up.
         */
        if (ip_rsvp_on) {
                ip_rsvp_on = 0;
                rsvp_on--;
        }
        return 0;
}

void
rsvp_input(struct mbuf *m, ...) /* XXX must fixup manually */
{
        int off, proto;
        __va_list ap;

        __va_start(ap, m);
        off = __va_arg(ap, int);
        proto = __va_arg(ap, int);
        __va_end(ap);

        if (rsvp_input_p) { /* call the real one if loaded */
                rsvp_input_p(m, off, proto);
                return;
        }

        /* Can still get packets with rsvp_on = 0 if there is a local member
         * of the group to which the RSVP packet is addressed.  But in this
         * case we want to throw the packet away.
         */

        if (!rsvp_on) {
                m_freem(m);
                return;
        }

        if (ip_rsvpd != NULL) {
                rip_input(m, off, proto);
                return;
        }
        /* Drop the packet */
        m_freem(m);
}